Auditory-visual integration in neonates: A signal detection analysis

Abstract

The ability of neonates to integrate auditory and visual information into a single percept was investigated using a signal detection methodology. Thirty-two infants (mean age = 4.6 days) were presented with an auditory stimulus (the word “baby” spoken once, or repeated four times) from either directly ahead (catch trials), or to the infant's side (signal trials); lateral displacements of 45° left or right, and 90° left or right were used. A video recording of neonates' oculomotor behavior during the experimental session was made for later independent scoring by two judges. The methodology enabled separate performance indices of sensitivity and response bias to be calculated for both ipsilateral and contralateral eye turns. Subsequent analyses of these indices showed that while neonates displayed a significant bias toward not responding ( p < .001), ipsilateral eye turns occurred more frequently than expected by chance ( p < .001). The frequency of eye movements was not influenced by either the duration of the auditory stimulus, the degree of lateral displacement, or whether the sound was presented from the left or right of the midline. The methodological implications of these results are discussed in relation to previous investigations of auditory-visual coordination.